His conviction was later quashed and a retrial ordered after the Court of Appeal said a military judge had improperly pressured Sgt Nightingale into pleading guilty.

The new court martial heard police had found the weapon and ammunition during a search of his house, which he shared with another member of the SAS.

A special forces comrade told the retrial in Bulford, Wiltshire, that strict rules on possessing firearms applied to all personnel.

The soldier, named only as Soldier Y, said there was no exception or “turning a blind eye” to these orders within the SAS.

He said: "We have no dispensation nor have we had any."

Timothy Cray, prosecuting, asked: "Given the nature of your unit was there any special exemptions in terms of members of the unit having firearms for their own use that had not been issued by the unit?"

Soldier Y replied: "None whatsoever."

Mr Cray continued: "The allegations against Sgt Nightingale are that he had an unauthorised firearm in his bedroom of his single service substitute accommodation and 338 rounds of live ammunition.

"From a unit point of view, if that were true, how seriously would such a breach be regarded?"

Soldier Y replied: "It would be regarded as a gross breach bearing in mind the nature and quantity of the ammunition that was allegedly found at the defendant's house."

Sgt Nightingale's family, including wife Sally and father Humphrey, were in court to support him.